JP5359313B2 - Motor control device - Google Patents

Description

  The present invention relates to a motor control device that controls the rotational speed of a motor based on an output signal of an encoder attached to the motor.

Conventionally, as shown in FIG. 11, the rotation speed of the motor (3) is detected by directly attaching the encoder (4) to the output shaft (31) of the motor (3).
As shown in FIG. 12, the adapter shaft (32) is connected to the output shaft (31) of the motor (3), and the encoder (4) is attached to the adapter shaft (32).

In any of the mounting structures, due to assembly errors, as shown in FIG. 13, there is a deviation (eccentricity) between the shaft core C1 of the output shaft (31) of the motor (3) and the shaft core C2 of the bearing of the encoder (4). May occur.
In such a case, even if the rotation speed of the motor is constant as shown in FIG. 14 (a), the rotation speed obtained by calculation from the output signal of the encoder is as shown in FIG. 14 (b) per rotation of the motor. A sinusoidal ripple is generated at a rate of once.

When the speed control of the motor is performed in such a state, the speed control system executes the feedback control so as to cancel the speed ripple. Therefore, the rotational speed obtained by calculation from the output signal of the encoder as shown in FIG. Is a constant value, but by such control, a sinusoidal ripple is generated in the rotational speed of the motor as shown in FIG.
As a result, for example, in an elevator using a motor as a drive source, the speed ripple of the motor is transmitted to the passenger car via the rope, causing a problem of worsening the riding comfort.

Accordingly, it has been proposed to eliminate the speed ripple by optically measuring the eccentricity between the motor and the encoder and correcting the speed control of the motor (Patent Document 1).
In addition, there has been proposed a technique for suppressing a ripple generated in the output torque of a motor by an antiphase torque command (Patent Documents 2 and 3).

JP 2007-183255 A JP 2002-223582 A JP 2005-206343 A

However, in the technique of optically measuring the amount of eccentricity between the motor and the encoder, there is a problem that the structure for measurement is complicated.
In addition, the technology that suppresses the ripple generated in the output torque of the motor by the torque command with the opposite phase is only to suppress the torque ripple. Therefore, when the load torque changes, it is also necessary to change the correction amount of the torque command. There is a problem that the control becomes complicated.

  The objective of this invention is providing the motor control apparatus which can prevent the speed ripple resulting from eccentricity, without measuring the eccentricity amount between a motor and an encoder directly.

A motor control device according to the present invention detects a motor rotation speed based on an output signal of an encoder attached to a motor, and generates a torque command according to a deviation between the detected motor rotation speed and the speed command. Because
Waveform detection means for generating a speed command for rotating the motor at a constant speed in the compensation amount determination mode, thereby detecting a waveform appearing in the torque command;
From the waveform detected by the waveform detection means, a disturbance component included in the encoder output signal due to the misalignment between the motor and encoder shaft is derived, and a compensation amount for canceling the derived disturbance component is determined. Compensation amount determining means to perform,
Compensating means for compensating the output signal of the encoder by the compensation amount determined by the compensation amount determining means in the normal operation mode.

  According to the motor control device of the present invention, first, in the compensation amount determination mode, a speed command for rotating the motor at a constant speed is generated, and thereby a torque command corresponding to the speed command is generated. Here, if there is a deviation between the axis of the motor and the axis of the encoder, a sinusoidal disturbance corresponding to the magnitude and direction of the deviation of the axis will occur in the output signal of the encoder. And by speed control according to the speed command, the torque command fluctuates in a sine wave shape so that the output signal of the encoder becomes a constant value.

  With the above torque command, the rotational speed of the motor fluctuates in a sine wave shape with a 90 ° phase shift from the torque command. The fluctuation component of the rotational speed of the motor has an antiphase relationship with the disturbance component included in the output signal of the encoder. Therefore, by compensating the encoder output signal to cancel out this disturbance component, a speed detection signal obtained from the encoder can be generated when there is no deviation between the motor shaft core and the encoder shaft core. I can do it.

  Therefore, the waveform detection means detects the waveform appearing in the torque command, and the compensation amount determination means determines whether the compensation amount determination means is based on the torque command waveform detected by the waveform detection means, due to the deviation of the axis between the motor and the encoder. The disturbance component included in the output signal is derived, and a compensation amount for canceling the derived disturbance component is determined.

In the normal operation mode in which the motor rotational speed follows the arbitrary speed command, the encoder output signal is compensated by the compensation amount determined by the compensation amount determining means, and the speed feedback signal includes the core of the motor and the encoder. Correction according to the deviation is added.
Therefore, even if a deviation exists between the motor shaft and the encoder shaft, the rotational speed of the motor does not fluctuate sinusoidally with respect to a constant speed command.

In a specific aspect of the present invention, the rotation angle of the motor with the Z-phase pulse obtained from the encoder as the origin is x, the phase is θ, the amplitude is K, and the waveform detected by the waveform detection means is Ksin (x + θ). When represented, the compensation amount determination means comprises phase determination means for determining the compensation amount to be subtracted from the output signal of the encoder as -Acos (x + θ), where A is the amplitude.
Here, the waveform detection means can detect the phase θ of the waveform appearing in the torque command with reference to the Z-phase pulse obtained from the encoder.

  In a more specific aspect, the compensation amount determining means changes the amplitude of the compensation amount under a rated motor rotation speed after the phase of the compensation amount is determined by the phase determining means, and in the process, a torque command Amplitude determination means is provided for determining the amplitude of the compensation amount at the time when the phase of the compensation amount is reversed with respect to the phase of the compensation amount as the amplitude of the compensation amount used in the normal operation mode.

  In still another specific aspect, the compensation amount determining means includes an operation means for changing the amplitude of the compensation amount at a constant motor rotation speed, and a phase of the torque command in the process of changing the amplitude of the compensation amount. Detecting means for detecting the amplitude of the compensation amount at the time when the phase is reversed with respect to the phase of the compensation amount, and amplitude setting means for setting the detected amplitude as the amplitude of the compensation amount used in the normal operation mode. It is.

  According to the motor control device of the present invention, it is possible to prevent the speed ripple caused by the eccentricity by correcting the speed feedback signal without directly measuring the eccentricity amount between the motor and the encoder. .

It is a block diagram which shows the structure of the motor control apparatus which concerns on this invention. It is a wave form diagram showing the change of the signal of each point in this motor control device. It is a wave form diagram showing the phase difference of the Z phase pulse obtained from an encoder, and a torque command. It is a block diagram which shows the structure of a general motor control apparatus. It is a wave form diagram showing a change of a signal of each point in a general motor control device in case a misalignment does not exist between a motor and an encoder. It is a block diagram explaining a structure in case a misalignment exists between a motor and an encoder in a general motor control apparatus. It is a wave form diagram showing the change of the signal of each point in case a misalignment exists between a motor and an encoder in a general motor control device. It is a flowchart which shows the procedure for determining the compensation amount in the motor control apparatus which concerns on this invention. It is a flowchart which shows the procedure for measuring automatically the phase of a compensation amount in the motor control apparatus which concerns on this invention. It is a flowchart which shows the procedure for identifying the amplitude of a compensation amount. It is a side view which shows the state in which the encoder is attached to the motor. It is a side view which shows the other state by which the encoder is attached to the motor. It is a front view showing a mode that misalignment exists between a motor and an encoder. It is a wave form diagram showing the change of the speed obtained by a calculation from a motor rotation speed and an encoder signal, when a misalignment exists between a motor and an encoder. It is a waveform diagram showing the motor rotation speed obtained as a result of speed control, and the change of the speed obtained by calculation from an encoder signal.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
The motor control device is generally composed of a feedback control system as shown in FIG. 4, and includes an inverter (2) for driving the motor (3) and a rotary type for detecting the rotational speed of the motor (3). An encoder (4) and a control circuit (9) for feedback controlling the inverter (2) based on the output signal of the encoder (4) are provided.

  The output signal of the encoder (4) is supplied to the speed calculator (7) that constitutes the control circuit (9) to create the speed feedback signal g. Then, a deviation between the speed feedback signal g and the speed command a is generated and supplied to the controller (5). As a result, a torque command b is generated, and the torque command b is sent to the inverter (2).

  If there is no deviation between the axis of the motor (3) and the axis of the encoder (4), for example, if the speed command a is constant as shown in FIG. 5, the torque command b is constant in the steady state. The motor (3) rotates at a constant rotational speed c. As a result, the speed feedback signal g is also constant.

However, if there is a deviation between the shaft core of the motor (3) and the shaft core of the encoder (4), the encoder (4) is in response to the output of the pulse generator (8) as shown in FIG. The configuration is such that a disturbance f (x) corresponding to the amplitude and phase of the misalignment is added.
In this case, even if the speed command a is constant as shown in FIG. 7, the feedback control works so as to maintain the output signal of the encoder (4) at a constant value. A sinusoidal waveform that fluctuates in the same cycle.

  Here, the phase of the motor (3) is represented by θ, the amplitude is represented by K, and the torque command b is represented by Ksin (x + θ). The rotation angle x of the motor (3) can be obtained by counting the number of encoder pulses (A phase pulse and B phase pulse) with reference to the Z phase pulse obtained from the encoder (4).

When the torque command b is sent to the inverter (2), the rotational speed c of the motor (3) is sinusoidal with a phase difference of 90 degrees from the fluctuation of the torque command b as shown in FIG. Will fluctuate. The fluctuation component of the rotational speed c of the motor (3) has an opposite phase relationship with the disturbance component f (x) included in the output signal of the encoder (4).
As a result, the speed feedback signal g obtained from the speed calculator (7) has a constant value.

  As described above, in the conventional general motor control device, the rotational speed of the motor (3) is caused by the misalignment between the motor (3) and the encoder (4) even though the speed command a is constant. There was a problem that fluctuated sinusoidally.

On the other hand, in the motor control apparatus according to the present invention, as shown in FIG. 1, the control circuit (1) for controlling the inverter (2) is provided with a compensation element (6) before the speed calculator (7). doing.
In the encoder (4) attached to the motor (3), a disturbance f (x) due to misalignment between the motor (3) and the encoder (4) is added to the output signal of the pulse generator (8). The output signal of the encoder (4) is compensated through the compensation element (6) constituting the control circuit (9), and then supplied to the speed calculator (7) for speed compensation. A feedback signal g is created. Then, a deviation between the speed feedback signal g and the speed command a is generated and supplied to the controller (5). As a result, a torque command b is generated, and the torque command b is sent to the inverter (2).

The compensation element (6) of the control circuit (1) inverts the compensation amount corresponding to the disturbance f (x) and adds it to the output signal of the encoder (4).
Here, the rotational speed of the motor (3) is generated when a constant speed command is given by a conventional general motor control device when there is a misalignment between the motor (3) and the encoder (4). Since the torque command Ksin (x + θ) has a phase difference of 90 degrees, the disturbance f (x) is represented by −Acos (x + θ), where the amplitude is A.

  The phase θ of the torque command Ksin (x + θ) can be defined with reference to the Z-phase pulse obtained from the encoder as shown in FIG. That is, a zero cross point at which the torque command changes from a negative value to a positive value is detected, and the motor rotation angle from the detection time until the Z-phase pulse is generated is defined as θ.

  The compensation element (6) has only to invert the signal having the same amplitude and phase as the disturbance f (x) and add it to the output signal of the encoder (4), so that the compensation to be subtracted from the output signal of the encoder (4) The quantity is expressed as -Acos (x + θ).

  FIG. 8 shows a procedure for determining the compensation amount. First, in step S1, the motor rotation speed is set to a low speed for determining the compensation amount (frequency lower than the speed control response), and a speed command is generated. Next, in step S2, the phase θ of the compensation amount is determined, and in step S3, the amplitude A of the compensation amount is identified. Thereafter, the phase θ of the compensation amount is stored in the nonvolatile memory, the amplitude A of the compensation amount is stored in the nonvolatile memory, and the adjustment completion flag is set to ON.

  When the motor rotation speed is set to a frequency lower than the speed control response, no ripple occurs in the motor rotation speed calculated from the encoder output signal, and instead the torque command has a ripple. If the phase of the torque command with reference to the phase pulse is detected, the phase θ of the compensation amount can be determined.

  Therefore, in the procedure for determining the phase θ of the compensation amount, first, in step S21 in FIG. 9, the count value n is initially set to 0, and then in step S22, the AC component is calculated from the torque command using a high-pass filter. The result is taken as a new torque command. In step S23, torque command filtering is performed to remove noise.

Subsequently, in step S24, it is determined whether the torque command has a positive slope and the torque command has passed the zero cross point. If no, the process returns to step S22 and the same processing is repeated. Thereafter, when it is determined as YES in step S24, the process proceeds to step S25, and counting of the A-phase pulse and B-phase pulse of the encoder is started.
Next, in step S26, it is determined whether or not the encoder Z-phase pulse has been detected. If no, the process returns to step S25 to continue counting the A-phase pulse and the B-phase pulse.

Thereafter, when a Z-phase pulse is detected in step S26, the process proceeds to step S27, and the count values of the A-phase pulse and the B-phase pulse are divided by the number of encoder pulses, and the result is set as a sample value θn.
Subsequently, after incrementing the count value n in step S28, in step S29, it is determined whether or not the count value n has reached a predetermined number of samples (for example, 5). If no, the process returns to step S22. Repeat the same procedure.

Thereafter, when it is determined as YES in step S29, the process proceeds to step S30, the average value of θn is calculated, and the result is determined as the phase θ of the compensation amount.
Note that the number of samples for calculating the average value of θn is not limited to five and can be set to an arbitrary value.

In order to identify the amplitude A of the compensation amount, for example, the following search procedure can be employed.
That is, when the motor is rotated at the rated rotation speed, the compensation amount amplitude is increased by a certain increment, and when the torque command is observed in the process, overcompensation occurs when the amplitude exceeds a certain value. The quantity waveform has an opposite phase, and the phase of the torque command is reversed to suppress this. When the phase is reversed, the next step is to reduce the amplitude by setting a small increment. When the amplitude falls below a certain value, the amount of compensation is insufficient, so the phase of the torque command is reversed again. Once the phase is reversed, the next step is to decrease the increment and increase the amplitude. By repeating this procedure, the value of the amplitude A will approach the true value as much as possible. Therefore, if the repetition is terminated when the step amount becomes a certain value or less, the value of the amplitude A at that time Can be determined as an identification result.

FIG. 10 shows a procedure for identifying the amplitude A of the compensation amount by the above method. First, in step S31, the amplitude A is initialized to 0, and in step S32, the amplitude fluctuation range ΔA is set to an initial value (for example, 50). ).
Next, in step S33, it is determined whether or not the absolute value of the amplitude fluctuation range ΔA is smaller than a predetermined value. If no, the process proceeds to step S34 to add the fluctuation range ΔA to the amplitude A and A large amplitude A is assumed.
Subsequently, in step S35, the motor control device is operated with the compensation amount as Acos (x + θ). In step S36, the phase of the compensation amount Acos (x + θ) and the torque command Ksin (x + θ) is compared.

In step S37, it is determined whether the phase of the torque command is reversed with respect to the phase of the compensation amount. If no, the process returns to step S34 and the same procedure is repeated.
Thereafter, when it is determined as YES in step S37, the process proceeds to step S38, the fluctuation range ΔA is multiplied by a predetermined coefficient (for example, −0.5), and the result is set as a new fluctuation range ΔA. Returning to S33, the same procedure is repeated.
As a result, when it is determined as YES in step S33, the process proceeds to step S39, and the amplitude A at that time is determined as the identification result.

  The initial value of the amplitude fluctuation range ΔA in step S32 is not limited to 50, and an arbitrary value can be set. The coefficient to be multiplied by the fluctuation range ΔA in step S38 is not limited to −0.5, and an arbitrary value can be set.

  The amplitude of the compensation amount according to the speed at which the motor accelerates or decelerates can be easily determined by converting the amplitude of the compensation amount at the rated rotational speed into a value proportional to the speed.

In the normal operation mode in which the motor rotational speed follows an arbitrary speed command, the compensation amount Acos (x + θ) having the amplitude and phase determined by the above procedure is set in the compensation element (6) shown in FIG. Compensation is performed by subtracting the compensation amount Acos (x + θ) from the output signal of the encoder (4), and a speed feedback signal g is generated from the result, and feedback control is executed.
Therefore, even if there is a deviation between the shaft core of the motor (3) and the shaft core of the encoder (4), as shown in FIG. 2, the rotational speed c of the motor (3) according to a constant speed command a. Is constant and does not fluctuate sinusoidally.

In addition, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim. For example, in the compensation amount determination mode, for example, only the phase θ is determined by the procedure shown in FIG. 9, and the amplitude A is configured to be finely adjusted manually in the compensation amount determination mode or the normal operation mode. It is also possible.
In addition, the motor rotation speed when determining the compensation amount can be set to a frequency higher than the speed control response. In this case, it is necessary to calculate the phase of the compensation amount based on the speed control response frequency. There is.

(1) Control circuit
(2) Inverter
(3) Motor
(4) Encoder
(5) Controller
(6) Compensation factor
(7) Speed calculator
(8) Pulse generator

Claims (3)

In a motor control device that detects a motor rotation speed based on an output signal of an encoder attached to the motor and generates a torque command according to a deviation between the detected motor rotation speed and the speed command.
Waveform detection means for generating a speed command for rotating the motor at a constant speed in the compensation amount determination mode, thereby detecting a waveform appearing in the torque command;
From the waveform detected by the waveform detection means, a disturbance component included in the encoder output signal due to the misalignment between the motor and encoder shaft is derived, and a compensation amount for canceling the derived disturbance component is determined. Compensation amount determining means to perform,
Compensating means for compensating the output signal of the encoder by the compensation amount determined by the compensation amount determining means in the normal operation mode, the compensation amount determining means,
When the rotation angle of the motor is x, the phase is θ, the amplitude is K, and the waveform detected by the waveform detection means is represented by Ksin (x + θ), the amplitude is A, and the compensation amount to be subtracted from the output signal of the encoder Phase determining means for determining a value of −Acos (x + θ);
After the phase of the compensation amount is determined by the phase determining means, the amplitude of the compensation amount is changed at a constant motor rotation speed, and the phase of the torque command is reversed with respect to the phase of the compensation amount in the process. Amplitude determination means for determining the amplitude of the compensation amount as the amplitude of the compensation amount used in the normal operation mode.
A motor control device characterized by comprising: In a motor control device that detects a motor rotation speed based on an output signal of an encoder attached to the motor and generates a torque command according to a deviation between the detected motor rotation speed and the speed command.
Waveform detection means for generating a speed command for rotating the motor at a constant speed in the compensation amount determination mode, thereby detecting a waveform appearing in the torque command;
From the waveform detected by the waveform detection means, a disturbance component included in the encoder output signal due to the misalignment between the motor and encoder shaft is derived, and a compensation amount for canceling the derived disturbance component is determined. Compensation amount determining means to perform,
Compensating means for compensating the output signal of the encoder by the compensation amount determined by the compensation amount determining means in the normal operation mode, the compensation amount determining means,
When the rotation angle of the motor is x, the phase is θ, the amplitude is K, and the waveform detected by the waveform detection means is represented by Ksin (x + θ), the amplitude is A, and the compensation amount to be subtracted from the output signal of the encoder Phase determining means for determining a value of −Acos (x + θ);
Operating means for changing the amplitude of the compensation amount under a constant motor rotation speed;
Detecting means for detecting the amplitude of the compensation amount at the time when the phase of the torque command is reversed with respect to the phase of the compensation amount in the process of changing the amplitude of the compensation amount;
Amplitude setting means for setting the amplitude detected by the detection means as the amplitude of the compensation amount used in the normal operation mode
A motor control device characterized by comprising: 3. The motor control device according to claim 1 , wherein the waveform detection unit detects a phase θ of a waveform appearing in a torque command with reference to a Z-phase pulse obtained from an encoder.

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